Normal human serum is tested for complement activity and certified to possess fully functional classical and alternative pathways of activation. Our NHS is also referred to in our product descriptions as the NHS complement standard. A functional lectin pathway is assumed to be present, but standard assays for all of its initiating components (ficolins, MASPs, and MBL) have not been established. Therefore, we have not tested specifically for lectin pathway activity.
NHS was prepared from a large number of donors. Each unit of blood was collected without anticoagulants and each was individually tested for transfusion-transmissible diseases before pooling (see Precautions/Toxicity/Hazards below). After coagulation, the liquid portion was separated by centrifugation. The different units were pooled, filtered through a 0.22 µm filter, aliqoted and frozen at -80oC.
All testing for complement activity was performed on the subsequently thawed samples to guarantee that the functional activity reported is what customers will receive when the samples are thawed. Complement activity is stable for several years if NHS is stored at -70oC or below continuously. A slight degradation of activity may be observed following additional freeze thaw cycles.
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